1. Field of the Invention
The invention relates to an ocular focus device, and more particularly to an ocular focus device for a sight.
2. Description of the Related Art
Referring to FIG. 1 and FIG. 2, a conventional ocular focus device 1 for a sight comprises an ocular housing 10, an ocular lens tube 20, a first ocular lens 31, a second ocular lens 32, a spacing ring 40, a press ring 50, a stop ring 60, a first sealing ring 71, a second sealing ring 72, and an ocular rubber member 80.
As shown in FIG. 2, the ocular housing 10 comprises an inner threaded portion 11.
As shown in FIG. 1 and FIG. 2, the ocular lens tube 20 comprises an outer threaded portion 21, an inner threaded portion 22, a thread-void groove 23, a first receiving groove 24, and a second receiving groove 25. The outer threaded portion 21, thread-void groove 23, and second receiving groove 25 are formed on an outer surface of the ocular lens tube 20. The inner threaded portion 22 and first receiving groove 24 are formed on an inner surface of the ocular lens tube 20. The thread-void groove 23 is adjacent to the outer threaded portion 21 and is formed between the outer threaded portion 21 and the second receiving groove 25.
As shown in FIG. 1, the press ring 50 and stop ring 60 comprise an outer threaded portion 51 and an outer threaded portion 61, respectively.
The following description is directed to assembly of the ocular focus device 1.
As shown in FIG. 2, the first sealing ring 71 is fit in the first receiving groove 24 of the ocular lens tube 20. Here, the first sealing ring 71 can provide airtight and water-resistant functions. The first ocular lens 31 is then disposed in the ocular lens tube 20 and abuts the first sealing ring 71. The spacing ring 40 and second ocular lens 32 are then disposed in the ocular lens tube 20. Here, the spacing ring 40 is abutted between the first ocular lens 31 and the second ocular lens 32, fixing a separated distance therebetween. The press ring 50 is then revolved in the ocular lens tube 20 until abutting the second ocular lens 32. Here, the positions of the first ocular lens 31 and second ocular lens 32 in the ocular lens tube 20 can be fixed by the press ring 50. Then, the second sealing ring 72 is fit in the second receiving groove 25 of the ocular lens tube 20 and the ocular rubber member 80 is fit on the ocular lens tube 20. Here, the second sealing ring 72 can provide airtight and water-resistant functions and the ocular rubber member 80 can protect eyes of an operator. The stop ring 60 is then disposed in the ocular housing 10. Then, the ocular lens tube 20 is fastened in the ocular housing 10 and the stop ring 60 is fastened in the ocular lens tube 20. Here, the stop ring 60 is separated from the press ring 50.
When using the ocular focus device 1 to perform a focus operation, the operator can revolve the ocular lens tube 20, enabling the ocular lens tube 20 to rotate and move with respect to the ocular housing 10. At this point, the first ocular lens 31 and second ocular lens 32 disposed in the ocular lens tube 20 move with respect to the ocular housing 10, achieving a focus effect. Moreover, the rotating and moving range of the ocular lens tube 20 with respect to the ocular housing 10 is limited by the stop ring 60 and thread-void groove 23.
Nevertheless, the ocular focus device 1 has many drawbacks as follows. As many constituent members of the ocular focus device 1 are formed with threaded portions (such as, the inner threaded portion 11 of the ocular housing 10, the outer threaded portion 21 and inner threaded portion 22 of the ocular lens tube 20, the outer threaded portion 51 of the press ring 50, and the outer threaded portion 61 of the stop ring 60), manufacturing costs of the ocular focus device 1 are high. Moreover, as many of the constituent members of the ocular focus device 1 are formed with the threaded portions, the thickness or volume thereof cannot be reduced. Thus, overall weight and material costs of the ocular focus device 1 cannot be reduced. Additionally, as the focus operation of the ocular focus device 1 is accomplished by revolving the ocular lens tube 20, the moving speed of the ocular lens tube 20 (or the first ocular lens 31 and second ocular lens 32) with respect to the ocular housing 10 cannot match the revolving speed of the operator. Namely, the focus speed of the ocular focus device 1 is confined to a predetermined speed range.
Hence, there is a need for an ocular focus device with reduced manufacturing costs, size, and weight, increased focus speed, and enhanced operational convenience.